Buying properties with tax liens

Hi everyone, 

Yesterday, I had the pleasure of meeting a real estate investor from New York and we were able to discuss some of his real estate strategies. He told me that he gets a list of property owners who are delinquent on their taxes and whose properties are going to be placed in the auction. He contacts these owners prior to the auction date, and pays for their taxes and gives them an additional amount as an incentive. He told me that he has been using this strategy for 20 years and has been very successful. 

What are your thoughts on this strategy and have any of you actually used it and been successful?